Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Outline • Evolution – Origin of Life – Origin of Species • • • • Evolution Natural Selection Speciation Human origin – References SCBI 124 General Biology ORIGIN OF LIFE Chemical Evolution • The origin of life – Abiotic synthesis of small organic molecules (amino acids and nucleotides) – The formation of polymers (proteins and nucleic acids) – Packaging into protobionts – The origin of hertitable molecules. Origin of Earth • Earth – 4.6 Billion years ago (BYA) – 3.9 BYA; forming phase ended – 3.8 BYA; • The oldest rock on Earth (Issua, Greenland) • Atmosphere – Reducing atmosphere and “primitive soup” (Oparin and Haldane, 1920) – The origin of organic molecules (Miller and Urey, 1953) → amino acids, hydrocarbon compounds Artist’s conception of Earth approximately 3 billion years ago Deep-sea vents are rich in sulfur and iron. Miller and Urey’s experiment using reducing system of H2, CH4, NH3 and water. The Origin of Life • Abiotic synthesis of polymers – Polymers formed by dripping amino acid solution on hot sand, clay or rock. • Protobionts – An aggregate of chemicals inside membrane-like structure. (liposome) • RNA World – Ribozyme – RNA with catalytic function – Natural selection → on protobiont with RNA – DNA World (stable, more accurate replication) The Origin of Cells • Prokaryotes – Stromatolites 3.5 MYA layers of bacteria – The origin of electron transport system – The oxygen revolution (from cyanobacteria) 2.72.2 BYA (10% more than present day) The Origin of Cells • Eukaryotes – 2.7 BYA cholesterol, 2.2 BYA for simple alage, 2.1 BYA most agreed eukaryote – (Serial) Endosymbiosis: the origin of mitochondria and chloroplasts – Cytoskeleton: the origin of sexual reproduction – “You are what you eat” hypothesis The origin of eukaryotic cells through endosymbiosis events. 3.5 BYA fossilized stromatolites; Shark Bay, Australia Iron oxide of terrestrial rock suggested oxygen was in the air. The Origin of Multicellulars • Multicellulars – Algae, plants, fungi and animals • Early multicellulars – 1.2 BYA small algae (1.5 BYA by molecular clock) – 750-570 MYA → severe ice age (Snowball Earth hypothesis) • Colonies – Collections of cells, some become differentiated. Phanerozoic Proterozoic Homo Mammals Reptiles Cretaceous extinction 65.5 MYA Permian extinction Archaen Fish 251 MYA Cambrian 542-488.3 MYA Earth’s major crustal plates Laurasia and Gondwana Pangaea Continental drift SCBI 124 General Biology EVOLUTION IDEAS AND EVIDENCE Nothing makes sense in biology, except in the light of evolution. (T. Dobzhansky, 1973) Introduction • Natural selection as evolutionary process – Population changes over time, certain heritable traits can help organism leave offspring than other. • Evolutionary adaptation – An accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environment. Introduction • Evolution – Descent with modification – A change over time in the genetic composition of a population • Speciation: new species – A gradual appearance of all of biological diversity. A marine iguana, well-suited to its rocky habitat in the Galapagos Islands. Historical Context • Darwinism – Timing and logic – Resistance to the idea of evolution • Western culture: – Earth is a few thousand years old, populated by unchanging organisms. The historical context of Darwin’s life and ideas. Catastrophism • Fossils, Cuvier and catastrophism – Paleontology • The study of fossils developed by Georges Cuvier (1769-1832) • Catastrophism – Not believe in gradual evolution, strata boundaries came from catastrophism. – Sudden and violent changes (flood or drought) that can destropy many species. Fossils from strata of sedimentary rock: The Colorado river and the Grand Canyon. Lamarck’s Theory of Evolution • Jean-Baptiste de Lmarck – Evolutionary change explains the fossil record and organisms’ adaptations to their environments. • Changes occur, but no extinction. • Species only transformed. – How does evolution occur? • Use and disuse • Inheritance of acquired characteristics – Innate drive Acquired traits cannot be inherited: the bonsai. Darwin’s Research • The Origin of Species – Species change through natural selection • Darwin – Shrewsbury (western England) – University of Edinbrugh (medicine) – Cambridge University (clergyman) • John Henslow (botanist) • Robert FitzRoy (captain of HMS Beagle) The Voyage of the Beagle • What did Darwin find? – Various adaptation of plants and animals – Ecological diversity, from grassland to high mountain – South America temperate species are resembled species in the tropic, rather than Europe temperate species. The Voyage of the Beagle • What did Darwin find? – Fossils were distinct, but resemble those living species of the continent. – Geologic processes can change the landscape • Principles of Geology (Chales Lyell, 1830) – Galapagos island species Armadillos (living species) Megatheres (extinct species) Capibara (living species, small) Capibara (extinct species, large) The voyage of HMS Beagle Darwin’s Focus on Adaptation • Adaptation and speciation – Could a new species arise from an ancestral form by the gradual accumulation of adaptations to a different environment? • Galapagos finches – Their beaks and behaviours are adapted to specific food found on their specific islands. Darwin’s Focus on Adaptation • The origin of species – 1840s • major features done, Darwin was in poor health. – 1844 • the long essay was written but unpublished. – 1858 • Alfred Russel Wallace wrote to Darwin – 1859 • Darwin published “The Origin of Species” Beak variation in Galapagos finches The Origin of Species • Descent with modification – Darwin’s view of life – Tree of life • Elephant evolution – Linnaeus taxonomy • Reflect the branching history of the tree of life as species descended from their common ancestors. Descent with modification: evolutionary tree of elephant Natural Selection • Definition – Natural selection is the differential success in reproduction that results from the interaction between individuals that vary in heritable traits and their environment. • Differential success in reproduction – The unequal ability of individuals to survive and reproduce. Natural Selection • Effects – Over time, natural selection can increase the adaptation of organisms to their environment. • If the environment change or individual move to new habitat, natural selection could sometimes give rise to new species. Camouflage as an example of evolutionary adaptation Natural Selection • Unit of evolution – A population is the smallest unit that can evolve. • Natural selection occurs through interaction between individual and environment, but individual do not evolve. • Population – A group of interbreeding individuals belonging to a particular species and sharing a common geographic area. Natural Selection • Life as Darwin see it – Life evolve through gradual accumulation of small changes. • Natural selection operates in various contexts over time as can be seen in geological evidence and the entire diversity of life. • Measuring evolution – Relative proportions of heritable variations in a population over a succession of generations. Evidence of Evolution • Evolution can help answer questions – Why certain characteristics in related species have an underlying similarity even though they may have very different function. • Homology – Anatomical homologies • Comparative embryology – Molecular homologies • Biogeography • The fossil record Homology • Homology – Similarity resulting from common ancestry. – Anatomical homologies (comparative anatomy) • Comparison of body structures between species. Homology • Homology • Homologous structure – Variation on a structural theme that was present in their common ancestor. – Vestigial organs » Remnants of structures that served important functions in the organism’s ancestors. • Comparative embryology – The comparison of early stages of animal development, not visible in adult organisms. Homology • Homology – Molecular homologies • Similarity at the molecular level. All forms of life use the same genetic machinery of DNA and RNA. • Many share genes (bacteria vs human) – Homologies and the tree of life • Molecular homology can date back to the ancestral past. • Some homologies evolved just recently (tetrapods), 5digit limbs → nested pattern. • Organisms evolved from a common ancestor. Mammalian forelimbs: homologous structure Anatomical similarities in vertebrate embryos Comparision of a protein found in diverse vertebrates Biogeography • Biogeography – The geographic distribution of species. • Closely related species tend to be found in the same geographic region. • Distant region with same ecological niche occupied by different species (sometimes look similar). Biogeography • Biogeography • Australia – Australian marsupials have eutherian lookalike. (i.e. sugar glider and flying squirrel). – Convergent evolution (not homologous) • Endemic – Species that found no where else (Galapagos, Hawaii) Different geographic regions, different mammalian brands SCBI 124 General Biology SPECIES AND SPECIATION Outline • Species and speciation – What is species? – Species concepts – Speciation modes – Adaptive radiation – Tempo of evolution – Macroevolution – References What is Species? • Species – Latin word, species=kind or appearance • Real or artificial? – Real entity as species can recognize its own species. – Higher taxonomic levels are artificial. • Continuous or discrete – Discrete (morphologically distinct species) The Biological Species Concept • Biological species concept (BSC) – Ernst Mayr (1942) – Members of the same species are reproductively compatible. • A species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are unable to produce fertile offspring with other populations. The Biological Species Concept • Limitations of the BSC – Fossil (extinct species) – Asexual organisms – No information of reproduction = inconclusive – Has no potential to interbreed (geographically isolated) Similarity between different species (Left) The eastern meadowlark (Sturnella magna) (Right) The western meadowlark (Sturnella neglecta) Both are distinct species, their song and behaviour are different prevent interbreeding if they meet in the wild. Diversity within a species All human (Homo sapiens) can interbreed. Reproductive Isolation • Reproductive isolation – Factors that prevent members of two species producing viable, fertile hybrid offspring. • Many barriers can work together. • Gene flow restriction Prezygotic Barriers • Prezygotic barriers – Before the hybrid zygotes are formed. • • • • • Habitat isolation Temporal isolation Behavioural isolation Mechanical isolation Gametic isolation Postzygotic Barrier • Postzygotic barriers – After the hybrid zygotes are formed • Reduced hybrid viability • Reduced hybrid fertility • Hybrid breakdown Prezygotic isolation Postzygotic isolation Prezygotic isolation (cont) Morphological Species Concept • Morphological species concept – Similarity between members of species is greater than with other species. • Good for both sexual and asexual species; taxonomists use this for ages. • Bad for its subjectivity, lack of reproductive isolation data Paleontological Species Concept • Paleontological species concept – Morphological discrete characters found from fossils. • Good for fossil identification. • Bad for its lack of reproductive isolation data. Ecological Species Concept • Ecological species concept – Similar ecological niche (what they eat, how they live, etc.) • Good for both sexual and asexual organisms. • Bad for lack of reproductive data and different species could have similar niche. Phylogenetic Species Concept • Phylogenetic species concept – Same species with a unique genetic history (belong to the same clade; appear as monophyletic group) • Good for both sexual and asexual, even fossils; can distinguish sibling species (then confirmed with BSC) • Bad for its requirement of extensive information (time and money as well as man hours) Speciation • Speciation – The evolution of a biological species. – The origin of new species. – There are two ways gene flow between subpopulations can be interrupted. • Allopatric speciation • Sympatric speciation Allopatric Speciation • Allopatric speciation – Greek allos=other, patra=homeland – Gene flow interruption – When subpopulation divided with geographic barrier (or distance) • Barriers’ effectiveness depending on mobility of organisms (birds vs turtle vs plants). • Genetic differences accumulate over time (mutations) • Allele frequencies altered by selection, drift Harris’s antelope squirrel (Ammospermophilus harrisi) of the southern rim of the Grand Canyon. White-tailed antelope squirrel (Ammospermophilus leucurus) of the northern rim of the Grand Canyon. Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon. Birds and other organisms that can disperse across the Grand Canyon have not diverged into different species on opposite rims. Can divergence of allopatric fruit fly populations lead to reproductive isolation? Starch Population Starch flies tend to mate with other starch flies. The barrier is not absolute, some flies mate with other flies from different population. Maltose Population Maltose flies tend to mate with other maltose flies. Sympatric Speciation • Sympatric speciation – Greek syn=together, patra=homeland • How can reproductive barriers (reduction in gene flow) between sympatric populations evolve when members remain in contact? – Chromosomal mutation » Polyploidy, autopolyploidy, allopolyploidy – Nonrandom mating » Habitat differentiation » Sexual selection Sympatric speciation by autopolyploidy in plants One mechanism for allopolyploid speciation in plants Sympatric Speciation • Polyploid species – The goatbeard plants (genus Tragopogon) • Diploid species – T. dubius, T. pratensis and T. porrifolius • Tetraploid species – T miscellus (T. dubiusxT. pratensis) • Allopolyploid species http://ftp.funet.fi – T mirus (T. dubiusxT.porrifolius) – With ongoing hybridization with its parent species. The lake Victoria Only 12,000 years old, but there are 500 species of cichlid fishes. Similar genetically, suggested that they diverged just recently, probably from food preferences. Does sexual selection in cichlids result in reproductive isolation? Under normal light, females of both species mate with male of the same species. Under monochromatic orange light, females of both species mate indiscriminately resulting in hybrid and viable hybrids. Males and females of Pundamilia pundamilia and P. nyererei Mate choice based on male colouration by females is reproductive barrier. As prezygotic become breached in the lab it suggests that genetic different is small and the speciation occur just recently. Adaptive Radiation • Adaptive radiation – Evolution of many diverse species • In new environment with many ecological niches to occupy. • Same habitat, but after mass extinction (just what thought to happen 65 MYA, when dinosaurs gave way to mammals to diversify. – Hawaii archipelago – Australia Dubautia laxa Argyroxiphium sandwicense Dubautia linearis Dubautia waialealae Dubautia scabra Adaptive radiation of the silversword alliance came from only one species of tarweed about 5 million years ago (molecular analysis). The Tempo of Speciation • Gradualism – Descent with gradual modification (Darwin) – Little changes accumulate over time. – Species continuously adapted to the environment. • Punctuated equilibrium – Niles Eldredge and Stephen Jay Gould – Long stasis, punctuated by sudden change. Two models for the tempo of speciation Gradualism model Punctuated equilibrium model Macroevolution • Macroevolution – Evolutionary changes above species levels. – As small differences accumulated, it would become clear and more pronounced. • Evolutionary novelties – Exaptation • Structures that evolve for one thing, but have another function sometime later (feather and flying). Allometric growth Differential growth rates in human. Legs and arms lengthen more than head and trunk. Comparison of chimpanzee and human skull growth. Similar for both chimpanzee and human in fetus. In adult, human skull become rounded with little sloping whereas chimp skull become elongated wilth sloping face. Different Time Heterochrony Salamanders that live on tree have their digit development end sooner, giving more webbing to developed for tree climbing. Short, but more webbing Hox mutations and the origin of vertebrates Invertebrate with one copy of Hox complex First duplication occurred 520 MYA New set of genes with new role of backbone development. Second duplication 425 MYA yielding 4 set of Hox complexes made jaws and limbs development possible. SCBI 124 General Biology HUMAN ORIGIN Phylogeny of mitochondrial cytochrome oxidase II alleles in humans and the African great apes. 129 Hominins The earliest hominins Aegyptopithecus sp. Sahelanthropus tchadensis Orrorin tugenensis Ardipithecus kadabba Ardipithecus ramidus The Australopithecus genus Australopithecus anamensis Australopithecus bahrelghazali Australopithecus afarensis Australopithecus africanus Australopithecus garhi The Paranthropus genus Paranthropus aethiopicus Paranthropus boisei Paranthropus robustus The Homo genus Kenyanthropus platyops Homo habilis H. rudolfensis H. ergaster H. erectus H. floresiensis H. antecessor H. heidelbergensis H. neanderthalensis H. sapiens idaltu H. rhodesiensis H. cepranensis H. georgicus H. sapiens Paranthropus boisei (specimen KNM-ER 406, left) and Homo ergaster (specimen KNM-ER 3733, right) both lived in what is now Koobi For a, Kenya, about 1.7 million years ago. 131 132 Homo ergaster Homo habilis Homo rudolfensis 133 Homo sapiens Homo heidelbergensis Homo neanderthalensis Homo erectus 134 Phylogeny of Homo sapiens and its recent ancestors and extinct relatives 135 Australopithecus afarensis Laetoli Footprint 136 Neanderthal’s Last Rock Refuge • New evidence published in Nature http://news.bbc.co.uk/2/hi/science/ nature/5343266.stm – Neanderthal might have live up to 24,000 years ago (thought to be 30,000 years ago). • Gorham cave, Gibraltar, Germany. – Homo sapiens entered Europe about 40,000 years ago. Gorham cave 138 Nature (13 Sep 2006) Letters to Editor Phylogeny of Neanderthals and modern humans 139 Summary • Evolution – Darwin: descend with modification – Mechanism: natural selection – Resource: genetic variation – Diversity: speciation – Unit: population – Motto: • Gene mutates, population evolves References • Textbooks – Campbell, N. A. (2008). Biology. San Francisco, Pearson Benjamin Cummings. – Department of Biology (2008), Biology 1. Sukdisopa Publishing. Bangkok. • Resource and discussion – Biology Homepage • http://www.sc.mahidol.ac.th/scbi